One currently widespread approach for the preparation of isopropanol is hydration of propylene. Although it is an old technique to hydrate olefins in the presence of conc. sulfuric acid catalyst, corrosion by sulfuric acid is a problem.
Other currently widespread approaches include hydration in gas/liquid mixed phase using strongly acidic ion-exchange resins, hydration in gas phase using strongly acidic solid acid catalysts, and hydration by gas phase catalytic reaction using catalysts having heteropoly-acids or inorganic acids carried thereon.
It was also well known from the past to hydrogenate the carbonyl group of acetone to prepare isopropanol. Included are reduction using such reagents as lithium aluminum hydride and sodium boron hydride and catalytic reduction using hydrogen gas.
Several new proposals were made in recent years as disclosed in Japanese Patent Application Kokai Nos. 12729/1987 and 77338/1987.
At present, synthesis of isopropanol by hydrogenation of acetone does not commercially work in practice. As compared with the direct hydration of propylene, this route of synthesizing isopropanol from acetone resulting from oxidation of propylene requires one extra step and is unreasonable from a process aspect.
Now acetone is produced in great amounts as a by-product in the phenol manufacture by the cumene process. The acetone feed becomes surplus in industrial supply and draws attention as a drawback of the cumene process. Although acetone found a major use as a starting material to produce methyl methacrylate, the demand for acetone is reduced by the recent changeover of the starting material to produce methyl methacrylate to another material. It thus becomes necessary to ensure the economy of the cumene process to produce phenol by making efficient use of the surplus acetone by-product. One possible approach is to convert acetone into its derivative, that is isopropanol which is of great industrial value. This approach will aid in establishing the economy of the cumene process to produce phenol.
A variety of methods were known for the preparation of isopropanol from acetone as previously described. Regarding catalytic hydrogenation, however, only an unexpectedly small number of proposals are found. Industrial cost efficient production of isopropanol is a key factor for the feasibility of an isopropanol preparing process particularly when considered from the standpoint of assisting in establishing the economy of the phenol preparing cumene process as intended in the present invention. Industrial isopropanol production has not been well established in this sense.